New study confirms that less water consumption in the vineyard can result in better grapes

As local farmers are well aware, Mother Nature can be cruel in administering her gifts.

This was the case on the night of September 11 when the Emeritus Vineyards team in Sevastopol smelled raindrops as they plucked the pinot noir grapes to enter the cellar’s premium wine.

While any rain is appreciated during an exceptional regional drought, the rainfall came at an inopportune time for the winery which would complete its harvest a week later, said Riggs Lokka, deputy vineyard manager.

“Suddenly at 1:15 am, he just fell,” Lokka recalls.

The episode brought to light the conditions in which the winegrowers operate: their industry faces a prolonged era of water scarcity in which the winegrowers do not want to put a drop of water more on their vines than necessary.

The use of water by local agriculture is increasingly monitored. Three of Sonoma County’s 14 groundwater ponds are under increased monitoring and regulation. These areas must be sustainable within 20 years, which means that there will be no significant drop in water tables from year to year. In addition, so far this year, state regulators have ordered more than 1,800 water rights holders in the Russian River watershed to stop water diversions unless they don’t get waivers.

But the oversight comes as academic research shows less water is better for the grape harvest, which was valued at $ 357 million in 2020 in Sonoma County. It can even improve the quality of the grape. A UC Davis study published earlier this month found that winegrowers in our area can use less water on vines without affecting crop yields or quality.

Research published in the journal Frontiers in Plant Science found that vineyards can use 50% of the irrigation water normally used without degrading the flavor, color and sugar content of the fruit.

Researchers focused on cabernet sauvignon at a Napa Valley research vineyard over two growing seasons: a rainy in 2019 and a hyper-arid in 2020. The team looked at how much water was lost in the atmosphere by the wine system depending on the canopy. Cut. The weekly tests used irrigation to replace 25%, 50% and 100% of what had been lost by the crop due to evapotranspiration, which is the process by which water evaporates from the vine as well. than the ground.

“This is an important finding,” said Kaan Kurtural, professor of viticulture and oenology at UC Davis who led the study. “We don’t necessarily have to increase the amount of water supplied to the vines.

There has been a constant debate for years over whether local vineyards should switch to dry farming, where natural rainfall, not irrigation, is used to produce a crop. Although some local wineries are dry grown, Kurtural said such a process would not be financially viable for the entire Golden State industry.

“In California, it won’t be economically feasible for our system,” he said. “Our system offers the best performance at the lowest cost. “

Even without adopting dry farming practices, many wineries in the North Coast, America’s most prized growing region, use significantly less water due to water scarcity as well as quality benefits. grape, said Mark Greenspan, a consultant from Windsor who has a doctorate in agricultural engineering.

“The people we work with have done a good job of minimizing irrigation anyway,” said Greenspan. “And that mainly delays the irrigation… in a lot of cases we haven’t seen any irrigation at all. “

Joe Dutton, co-owner of his family’s Dutton Ranch in Green Valley near Sevastopol, said about a third of their 1,200-acre vineyard is dry-cultivated. The farm has a mixture of wells and reservoirs to draw water for irrigation. Dutton noted that there was little water due to the lack of winter rains to irrigate last year.

“We’re in West County here where water has been scarce anyway,” Dutton said. “We have learned to grow crops with minimal water all of our lives. When you get to the west of Route 116, you find yourself in some pretty rare water situations.

Greenspan tries to help his clients delay watering during the growing season for as long as they can. Wine-growing areas closer to the Pacific Ocean and San Pablo Bay are more suited to using less irrigation than those further inland.

But this year, some vineyards that would typically be irrigated in early August received water in mid-July, he said. Some of these farms would likely run out of water before harvest.

Soil moisture is a determining factor in deciding whether or not to irrigate, Greenspan said. “In my mind, it was really the moisture in the soil that allowed us to apply irrigation precisely and prevent over-irrigation,” he said. “For me it is the best tool and always will be.”

Lokka can easily access his soil moisture readings on his smartphone via an app linked to sensors to software provided by Agrology, a startup working with a few vineyards in Napa, Sonoma and Mendocino counties. The company, which has offices in Sonoma County and Virginia, aims to help wineries monitor not only irrigation but also smoke levels to give farmers a better understanding of just how bad their harvest can be. prone to smoke.

“I can see the moisture level in my soil. They (the software) tap into the irrigation system. They can see exactly how you turn on the water and when you don’t turn on the water, ”said Lokka, who added that he particularly appreciates the smoke data because the smell of smoke in the local culture has been an emerging issue in recent years given how this affects quality.

Lokka said he usually only uses water to administer liquid fertilizer for the coming season, which he did this week, and for frost protection in low areas with overhead sprinklers. But drought forced emergency irrigation earlier this year.

The emeritus were forced to irrigate a few pockets of their vineyard around July 4 when the heat became excessive. “We just gave them a quick blow,” he said. “They have maybe 2 gallons of water per vine.”

You can reach editor Bill Swindell at 521-5223 or bill.swindell@pressdemocrat.com. On Twitter @BillSwindell.